1. Technical Field
Example embodiments of the present invention relate in general to technology that transmits and receives a frame in a wireless local area network (WLAN) system and more specifically to technology that transmits and receives a frame in an exposed node state or a blocked node state.
2. Related Art
With the development of information communication technologies, a variety of wireless communication technologies have been developed. Among these technologies, a wireless local area network (WLAN) includes technology that is used to make wireless connection to the Internet possible at homes, businesses, or in specific service providing areas using a portable terminal such as a personal digital assistant (PDA), a laptop computer, a portable multimedia player (PMP), a smart phone, a tablet PC, or the like, based on wireless frequency technologies.
A standard for WLAN technology has been developed as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard. WLAN technology according to IEEE 802.11a standard is operated based on an orthogonal frequency division multiplexing (OFDM) method, and may provide a transmission speed of up to 54 Mbps at a 5 GHz band. WLAN technology according to IEEE 802.11b standard is operated based on a direct sequence spread spectrum (DSSS) method and may provide a transmission speed of up to 11 Mbps at a 2.4 GHz band. WLAN technology according to IEEE 802.11g standard is operated based on the OFDM method or the DSSS method, and may provide a transmission speed of up to 54 Mbps at the 2.4 GHz band.
WLAN technology according to IEEE 802.11n standard is operated at the 2.4 GHz band and 5 GHz band based on the OFDM method, and may provide, when using a multiple input multiple output-OFDM (MIMO-OFDM) method, a transmission speed of up to 300 Mbps with respect to four spatial streams. The WLAN technology according to IEEE 802.11n standard may support a channel bandwidth of up to 40 MHz, and in this case, provide a transmission speed of up to 600 Mbps.
As such WLAN technology becomes more prevalent and its applications become more diverse, there is increasing a demand for new WLAN technology that can support a higher processing throughput than a data processing speed supported by IEEE 802.11n. Very high throughput (VHT) WLAN technology is one among IEEE 802.11 WLAN technologies proposed to support a data processing speed of 1 Gbps or higher. Among these, IEEE 802.11 ac has been developed as a standard for providing VHT in a band at 5 GHz or less, and IEEE 802.11ad has been developed as a standard for providing VHT in a band at 60 GHz.
In a system based on such WLAN technology, there is a problem that the performance of the WLAN system is degraded due to an exposed node and a blocked node.